International Journal of Coal Geology最新文献

{"title":"Geochemical and biological evidence for the presence of secondary microbial gas in anthracite: A case study in the songta block, northern Qinshui Basin, China","authors":"","doi":"10.1016/j.coal.2024.104564","DOIUrl":"10.1016/j.coal.2024.104564","url":null,"abstract":"<div><p>In general, the bioavailability of organic matter in coal decreases with increasing coal rank, and the current coalbed gas (CBG) present in anthracite (<em>R</em>_<em>o</em> <em>&gt;</em> 2.5%) is typically classified as a thermogenic gas. Recently, gas-production simulation experiments have revealed that native microorganisms could degrade complex organic matter in anthracite and then generate a certain amount of microbial gases. Therefore, the possibility of secondary microbial gas formation in anthracite under the current coal seam conditions requires further investigation. This study aimed to investigate the presence of secondary microbial gas in anthracite by analyzing and interpreting gas and water samples from the Songta (ST) block of the northern Qinshui Basin using geochemical and biological evidence. The study indicates that the coalbed water is primarily recharged by surface freshwater, and the oxidation/reduction potential (ORP) and closed coefficient values indicate a relatively reductive coalbed water environment, and the low concentrations of NO₃⁻, SO₄²⁻, and Fe³⁺ indicate complete denitrification, sulfate reduction, and iron reduction, respectively, and these conditions can provide a favorable environment for microbial methanogenesis. The majority of the water samples are located to the left of the global meteoric water line (GMWL), and the formation of secondary microbial gas is likely responsible for this leftward shift. The geochemical characteristics of the gas samples indicate that the CBG in anthracite is predominantly thermogenic in origin, but its δ¹³C-CH₄ value is significantly lighter than the theoretical δ¹³C value of the thermogenic CH₄, which may be influenced by the mixing of microbial CH₄. In the ST block, geochemical evidence for the presence of secondary microbial gas in anthracite is directly provided by the observation of the positive δ¹³C values of gas-phase CO₂ (ranging from +8.19‰ to +20.21‰) and dissolved inorganic carbon (DIC) (ranging from +17.65‰ to +27.1‰) in the coalbed water. The microbial community composition indicates the presence of hydrolyzing bacteria, acidogenic bacteria, hydrogen-producing acetogenic bacteria, and CO₂-reducing methanogens in the coalbed water, and these microorganisms are capable of cooperatively completing the conversion of anthracite to microbial gas, thereby providing the biological evidence for the presence of secondary microbial gas. Additional studies indicate that metabolic activities with different functions may be separated from each other in underground coal seams (e.g., methanogenesis and methane oxidation) and jointly involved in the cycling of carbon, nitrogen, and sulfur, which can reform the early thermogenic CBG in anthracite, and that secondary microbial gas exists mainly as by-products of metabolic act","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141732329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular characterization of biochar and the relation to carbon permanence","authors":"","doi":"10.1016/j.coal.2024.104565","DOIUrl":"10.1016/j.coal.2024.104565","url":null,"abstract":"<div><p>Molecular compounds present in biochar carbon structure are studied from biochar produced from forest, food, and agricultural wastes and sewage sludge using pyrolysis gas chromatography mass spectrometry (Py-GC/MS). The results show that with increasing biochar production temperature (PT), the total pyrolysis yield decreases, and the macromolecular structure becomes more condensed with the aromatic linkages becoming less alkylated, hence indicating a stable carbon structure. These highly stable biochar samples consist predominantly of inertinite and have the entire random reflectance (R_o) distributions above the inertinite benchmark (IBR_o2%). The results are aligned with high carbon stability of high-temperature biochar. In contrast, biochar samples that were insufficiently carbonized and comprised of mainly semi-inertinitic biochar contain alkane traces, volatile compounds, and higher degrees of alkylation with aromatic linkages in their molecular structure. This indicates the more proneness to oxidative and microbial breakdown, and therefore a less condensed and less stable carbon structure. Additionally, occurrence of these compounds in inertinitic biochar indicate retention of free hydrocarbons within the biochar carbon structure. Complimenting microscopic and bulk geochemical data, Py-GC/MS data is additionally advantageous to assess the stability conditions of the biochar samples.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141693896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Multidisciplinary approach to facies analysis and paleoenvironmental reconstruction of the Cretaceous Second White Specks Formation, Eastern Margin of the Western Interior Seaway, Canada","authors":"","doi":"10.1016/j.coal.2024.104563","DOIUrl":"10.1016/j.coal.2024.104563","url":null,"abstract":"<div><p>The Cenomanian-Turonian strata of the Second White Specks (2WS) Formation on the cratonic margin of the Western Interior Seaway (WIS) are comprised of organic-rich, carbonate-siliciclastic successions. This study focuses on a carbonate-siliciclastic succession of the 2WS in two cored wells located on the eastern margin of the Cretaceous Interior Seaway. Based on sedimentary facies and organic/inorganic geochemistry representing distal and proximal sections of the 2WS, it was possible to interpret factors, including productivity, preservation, and dilution of the Organic Matter (OM). The results revealed eight subfacies and three main facies associations, including deep shelf calcareous mudstones and marlstones, and shallow shelf bioclastic limestones. The carbonaceous mudstones have high type II immature kerogen content and the bioclastic limestones have low organic content dominated by type III and degraded type II kerogen. The 2WS mineralogy primarily consists of calcite, clay minerals, and quartz, and is characterized by a low degree of physical and chemical diagenesis. Based on mineralogical analysis, carbonate is the dominant component, and its proportion is inversely associated with terrigenous silica content. There is a general increase in carbonates and a decrease in siliciclastics from the distal to the proximal sections within the study area. Lateral changes in physical and chemical properties of similar facies associations are mainly controlled by changes in water depth. The 2WS was deposited during a long-lived transgression comprised of higher order parasequences. Core logging data from multiple drillholes show that these parasequences have a general coarsening upward trend with an upward shift from pelagic (i.e., planktonic foraminifera and coccoliths) to benthic (i.e., <em>Inoceramus</em>) carbonate productivity. During deposition of the mudstone/marlstone facies association, a clear and oxygenated water column allowed for a high photosynthetic activity to occur within the photic zone, which is reflected in OM enrichment and higher micronutrient content, such as Zn and Ni, predominance of fecal aggregates, and planktonic foraminifera. In the mudstone/marlstone facies, oxygen deficient pore water conditions, which are reflected in the high redox-sensitive trace element concentrations such as V, contributed to the high degree of OM preservation. The 2WS along the eastern margin of the WIS was deposited on a low gradient carbonate ramp environment. The oxygenated broad ramp accommodated the bioclastic limestones, which are characterized by high benthic carbonate dilution rate that resulted in lower OM preservation potential. The shallow shelf setting was characterized by restricted wave energy and minimal fluvial input from the adjacent craton under temperate climatic conditions. This study contributes to our understanding about paleo-oceanography and hydrocarbon exploration in analogous epeiric seas and mixed siliciclastic‑ca","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141705398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of thermal intrusion on the Alum Shale from south central Sweden","authors":"Anji Liu ,&nbsp;Xiaowei Zheng ,&nbsp;Niels H. Schovsbo ,&nbsp;Qingyong Luo ,&nbsp;Ningning Zhong ,&nbsp;Hamed Sanei","doi":"10.1016/j.coal.2024.104560","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104560","url":null,"abstract":"<div><p>This study investigates the geochemical and petrological characteristics of solid bitumen in the DBH15/73 core from the Furongian (upper Cambrian) and Miaolingian (middle Cambrian) Alum Shale in Billingen, south central Sweden. At Billingen a &gt; 30 m thick Permian diabase (dolerite sill) intruded approximately 100 m above the Alum Shale that promoting the formation of solid bitumen in the uppermost half of the Alum Shale due to enhanced heat flow. The bitumen has been classified into bituminite/diagenetic solid bitumen (DSB), initial-oil solid bitumen (IOSB), and primary-oil solid bitumen (POSB) based on their genesis, morphology and random solid bitumen reflectance (BR_o). The Miaolingian shale, constituting the lower part of the Alum Shale, is immature and contains solely bituminite and DSB, with measured BR_o ranging from 0.40% to 0.48%. In contrast, the Furongian shale exhibits enrichment in IOSB and POSB and range from marginally mature to peak oil generation with towards the top of the section. Characteristics of uneven heating is seen in the IOSB (BR_o: 0.97–1.08%) including oxidation rims and abnormally high maturity surrounding fractures. The POSB (BR_o: 0.63–2.01%) is present not only in the Alum Shale but also in the overlying Ordovician Latorp limestone and the underlying Kakeled Limestone Bed, and shows flow structures which is further evidence for migration. The abundance of POSB and IOSB is determined through maceral point counting, revealing POSB as the dominant bitumen type (1.54–7.13 vol%), while IOSB constitutes the minority (0.05–0.31 vol%) within the Furongian shale. This distribution suggests rapid thermal evolution of organic matter within the oil generation window. Additionally, a reduction in free hydrocarbons (Rock-Eval S1), potential hydrocarbons (Rock-Eval S2), and unexpectedly low T_max was observed in the Furongian shale. Results indicate that hydrocarbon generation resulting from thermal intrusion contributes to the relatively low S2. Migration of POSB and generated oil to adjacent layers leads to the loss of S1, while the reduced Tmax may be attributed to high uranium content which weakens carbon chain bond energy. These anomalies result in an underestimation when evaluating thermal maturity and kerogen type conversion based on Rock Eval data alone.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141606161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Organic petrography, biomarkers, and stable isotope (δ13C, δD, δ15N, δ18O) compositions of liptinite-rich coals","authors":"","doi":"10.1016/j.coal.2024.104561","DOIUrl":"10.1016/j.coal.2024.104561","url":null,"abstract":"<div><p>Liptinite-rich coals were evaluated using organic petrography, biomarkers, and stable isotopes to investigate their origin and paleoenvironmental significance, particularly, to explore fractionation characteristics of stable isotopes (δ¹³C, δD, δ¹⁵N, and δ¹⁸O) between bulk coal, extractable organic matter (EOM), and extracted coal residue (ER). The samples were collected from Cenozoic coal seams from the Yunnan and Liaoning Provinces in China. The samples are characterized by the enrichment of different types of liptinite. The late Pliocene sample YNP (liptinite = 73.5%) is dominated by sporinite and bituminite, whereas the late Pliocene sample YND (liptinite = 65.5%) is characterized by isolated resinite particles and amorphous resinite. The liptinite in the Eocene sample SB (46.0%) is represented by blocky resinite with homogeneous morphology. The differences in distribution and morphology of liptinite are due to the different coal-forming plants and depositional environments, as indicated by the biomarker compositions. Biomarker results indicated that the sample YNP was formed mainly by Pinaceae and angiosperms under oxidizing conditions with bacterial/fungal degradation, whereas the sample YND was derived from the woody parts of gymnosperms with lower contributions of angiosperms under reducing conditions with low microbial activity. The sample SB predominantly originated from Cupressaceae/Pinaceae under reducing conditions with a lack of bacterial/fungal degradation.</p><p>The fractionations of δ¹³C, δD, δ¹⁵N, and δ¹⁸O between bulk coal, EOM, and ER in the liptinite-rich coals are different. The δ¹³C values of bulk coal, EOM, and ER are mostly controlled by precursor paleovegetation and isotopic composition of CO₂. The lower δ¹³C values of samples YNP and YND from the late Pliocene compared to that of the Eocene sample SB resulted from the change of palaeoconditions (e.g., δ¹³C of atmospheric CO₂, cooling, and decrease of CO₂ concentration). The δ¹³C values of EOM in the samples YNP and YND are about 3‰ lower than δ¹³C values of bulk coal/ER, whereas δ¹³C fractionation between EOM and bulk coal/ER is small (&lt; 0.8‰) in the sample SB, probably due to the very limited microbial/fungal degradation. The δD values of EOM are 50 to 90‰ lower than that of bulk coal/ER within the same sample, reflecting different isotopic compositions of monomeric compounds compared to the macromolecular matrix of kerogen most probably due to differences in H-isotope fractionation during biosynthesis. The δ¹⁵N of bulk coal and ER show limited fractionation (&lt; 0.5‰) and are mainly controlled by precursor paleovegetation and microbial induced degradation processes. The studied liptinite-rich coals yield higher δ¹⁸O values than those detected in humic coals. The difference","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141638132","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decoding paleomire conditions of paleogene superhigh-organic-sulfur coals","authors":"Tushar Adsul ,&nbsp;Molly D. O'Beirne ,&nbsp;David A. Fike ,&nbsp;Santanu Ghosh ,&nbsp;Josef P. Werne ,&nbsp;William P. Gilhooly III ,&nbsp;Paul C. Hackley ,&nbsp;Javin J. Hatcherian ,&nbsp;Bright Philip ,&nbsp;Bodhisatwa Hazra ,&nbsp;Sudip Bhattacharyya ,&nbsp;Ritam Konar ,&nbsp;Atul Kumar Varma","doi":"10.1016/j.coal.2024.104559","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104559","url":null,"abstract":"<div><p>Superhigh-organic‑sulfur (SHOS) coals (coals with organic sulfur content &gt;4 wt%) are unique coal deposits found at a few notable locations in the world. Specific peat accumulation and preservation conditions must be met to form SHOS coals. Organic sulfur is a major constituent of such coals, and it may have various sources depending on the prevailing paleomire conditions. Understanding such paleomire conditions sheds light on the formation mechanisms of SHOS coals. This investigation decodes the paleomire conditions of the Paleogene SHOS coals from Meghalaya, India, using sulfur isotopic compositions (<em>δ</em>³⁴S) of organic sulfur (<em>δ</em>³⁴S_OS) and pyritic sulfur (<em>δ</em>³⁴S_Py) along with organic petrography, pyrite morphology and trace element ratios. Thirty coal samples were collected from the Jaintia Hills in the east, Khasi Hills in the middle, and Garo Hills in the west of Meghalaya. The organic sulfur content in the Garo, Khasi, and Jaintia coals varies from 1.0 to 3.3 wt%, 1.4 to 13.8 wt%, and 1.0 to 7.2 wt%, respectively. Further, after separation from pyritic sulfur and sulfate sulfur phases, the organic sulfur content ranges from 54.4 to 69.2%, 63.8 to 79.9%, and 59.3 to 73.8%, in the Garo, Khasi, and Jaintia Hills, respectively, suggesting the SHOS nature of these coal samples. The <em>δ</em>³⁴S_Py varies from −29.3 ‰ to +5.7 ‰, −21.3 ‰ to +27.3 ‰, and  −12.1 ‰ to −4.3 ‰, in the Jaintia, Khasi, and Garo Hills, respectively, while the <em>δ</em>³⁴S_OS fluctuates from −4.6 ‰ to +3.7 ‰, −9.3 ‰ to +7.8 ‰, and − 9.0 ‰ to −5.0 ‰, respectively. The <em>δ</em>³⁴S values of pyrite and organic sulfur (OS) in Jaintia coals are ³⁴S depleted compared to seawater sulfate (+22 ‰), leading to fractionations in the range of −51.3 ‰ to −16.3 ‰ (mean − 31.6 ‰) and − 26.6 ‰ to −18.3 ‰ (mean − 23.1 ‰) for pyritic and organic sulfur (OS), respectively. Pyrite in Khasi coals show a relatively heavier <em>δ</em>³⁴S composition averaging at −20.5 ‰, whereas organic sulfur (OS) isotope compositions range from −31.3 ‰ to −14.2 ‰ with a mean of −22.6 ‰. Pyrite and OS in the Garo coals are depleted compared to seawater sulfate. Isotope variations in the Jaintia, Khasi, and Garo coals indicate microbial sulfate reduction (MSR) of seawater sulfate. Large isotopic fractionations between Eocene seawater sulfate and pyritic sulfur (<em>Δ</em>³⁴S_{SO4Eocene – pyrite} = up to −51.3 ‰; mean − 31.6 ‰) in Jaintia coals indicate their possible formation in the water column/near the sediment-seawater interface (open system) and also hint toward dissimilatory sulfate reduction pathways that prevailed under anoxic redox conditions. However, mean values of <em>Δ</em>³⁴S_{SO4Eocene – pyrite} (−20.5 ‰) in the Khasi coals imply pyrite formation deeper in the sediments (more closed system) under d","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141582360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Weathering-induced organic matter enrichment in marine-continental transitional shale: A case study on the early Permian Taiyuan Formation in the Ordos Basin, China","authors":"","doi":"10.1016/j.coal.2024.104562","DOIUrl":"10.1016/j.coal.2024.104562","url":null,"abstract":"<div><p>A comparative analysis of the factors controlling organic matter (OM) enrichment between marine-continental transitional (transitional hereafter) and marine or lacustrine shales is lacking. The early Permian Taiyuan Formation in the Ordos Basin, deposited during a shift from marine to continental settings in northern China, provides a unique opportunity to unravel the differences in OM enrichment mechanisms among these shales. The Taiyuan Formation is characterized by high TOC content (average 4.50%) and kerogen type II₂-III. Most samples are thermally mature with a few high to post-mature samples relating to the Late Jurassic–Early Cretaceous Yanshanian magmatism. Rare earth elements and yttrium (REY) are dominated by light- and medium-types enrichments, with distinctly positive Gd anomaly, likely due to seawater incursion. A warm and humid climate prevailed during deposition of the Taiyuan Formation, consistent with the tropical-subtropical location of the North China Plate in the early Permian. The climatic conditions promoted intense continental weathering as reflected by high Th/Sc ratios, chemical index of alteration values, and feldspar alteration to scaly kaolinite. The V/(V + Ni) ratio is inconsistent with the other redox proxies, presumably due to variations in the redox buffer supply in the transitional facies (e.g., OM and pyrite), varying burial rates and dissimilar redox potential of different elements. Hence, this proxy should be interpreted with caution in such settings. Most redox proxies indicate oxic bottom water during deposition of the Taiyuan Formation transitional shale, in contrast to typical OM enriched marine and lacustrine shales where redox stratification or euxinic conditions are common. Instead, the dominant factor for OM enrichment in transitional shales appears to have been a high influx of terrestrial weathering products, including abundant higher-plants OM, associated with preservation of OM due to rapid burial. This process minimizes the detrimental effects of oxic conditions on OM accumulation in the transitional shale facies. This mechanism may hold relevance for analogous basins elsewhere.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141703618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sulfur stable isotopes in Paleogene coals of Northeast India","authors":"Vivek Kumar ,&nbsp;Dibyendu Paul ,&nbsp;Sudhir Kumar","doi":"10.1016/j.coal.2024.104550","DOIUrl":"10.1016/j.coal.2024.104550","url":null,"abstract":"<div><p>Sulfur stable isotope signatures are instrumental in tracing the sources and tracking the movement of sulfur in different environmental compartments, besides providing vital insights into the origin and transport dynamics. Sulfur stable isotope composition in coal can give valuable information regarding sulfur sources and the process of sulfur incorporation in coal. The present study was conducted to determine the total sulfur content and sulfur isotopic composition for bulk sulfur (bulk S δ³⁴S) in Oligocene and Eocene coal samples from coal mines and a few coal stockings in northeast India. The results revealed that the total sulfur content in coal samples varied between 1.03 and 4.80 (wt%) with an average value of 2.64 wt%. The bulk S δ³⁴S in coal samples exhibited a wide range between −4.66 ‰ to 14.78 ‰ (VCDT). Oligocene coal samples from mines in Arunachal Pradesh, Assam, and Nagaland were enriched with heavier sulfur isotopes relative to Eocene coal samples from the Jaintia Hills region of Meghalaya. A moderate positive correlation was observed in the Oligocene coal samples, in contrast to the moderate negative correlation found in the Eocene coal samples. The bulk S δ³⁴S values and sulfur content in coal samples from coal stockings matched closely with Assam and Meghalaya mine samples. The findings of this study can be used to track the sources and movement of coal sulfur in various environmental compartments, besides providing valuable information about sulfur sources, the process of sulfur incorporation in coal, and the depositional environment.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141403976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights on the regional thermal evolution from semianthracite petrology of the Fengfeng coalfield, China","authors":"Na Wang ,&nbsp;Joan S. Esterle ,&nbsp;Sandra Rodrigues ,&nbsp;James C. Hower ,&nbsp;Shifeng Dai","doi":"10.1016/j.coal.2024.104548","DOIUrl":"10.1016/j.coal.2024.104548","url":null,"abstract":"<div><p>Igneous intrusions induce alterations in coal and minerals. Alteration degree depends upon the in-situ coal rank and maceral composition, the intrusion temperature, heat source proximity, and intrusion size. In the Permo-Carboniferous Fengfeng coalfield, coal rank increases over some 50 km distance south to north from high volatile bituminous coal to anthracite. The coal seams were commonly intruded, and the regional elevation of rank was augmented by Jurassic-Cretaceous igneous intrusions, not just burial coalification. The petrographic examination of a semianthracite from the Dashucun mine in the north of the Fengfeng coalfield shows development of coke microstructure and increased reflectance approaching the dike in the No. 2 Seam. Based on 11 samples at 50-cm horizontal intervals, random vitrinite reflectance value (R_r) declines from 5.41% at the contact to the background value of 2.05% at 5-m distance from the contact. Towards the dike, vitrinite anisotropy increases and the microtexture shows development of circular, coarse mosaic, and ribbon anisotropic coke textures and devolatilization vacuoles. Natural coke textures respond to an estimated temperature &gt; 570 °C at the intrusion/coal contact. However, the occurrence of coke structures within a semianthracite reveals a local and regional thermal evolution. Coke textures suggest that coal rank was high volatile A bituminous coal at the time of intrusion. This has implications for burial history, heating, and subsidence rates. Assuming a paleogeothermal gradient of 40 °C/km, high volatile A bituminous coal (1% R_r) would have been buried to 3 km at the time of the Jurassic intrusion. The intrusion metamorphosed high volatile bituminous coal to natural coke and subsequent larger-scale regional metamorphism then metamorphosed the coal to semianthracite.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141408515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Organic petrology and geochemistry data reveal depositional and thermal history of coal in the Guaduas formation, Colombian Eastern Cordillera","authors":"L. Camacho-Aristizabal ,&nbsp;L. Burnaz ,&nbsp;L. Castro-Vera ,&nbsp;L. Mojica Silva ,&nbsp;R. Littke","doi":"10.1016/j.coal.2024.104549","DOIUrl":"10.1016/j.coal.2024.104549","url":null,"abstract":"<div><p>Colombia is a country rich in coal deposits; however, there are few published studies characterizing these coals in detail from a scientific perspective. This study investigates the thermal maturity and depositional environment of a coal seam from the Guaduas formation (Maastrichtian-Paleocene) of the Eastern Colombian Cordillera Basin, providing insight into burial and temperature history and changes in the depositional environment over time. This three-meter-thick hard coal seam reflects about 20 m of former peat deposition, representing a period of roughly 10.000 years.</p><p>Five large, fresh samples (A to E) were collected from the seam every thirty centimeters and divided into seventeen sub-samples analyzed using organic petrological methods, Rock-Eval pyrolysis and organic geochemistry. Different thermal maturity- and depositional environment-related parameters have been determined. Results reveal a maturity of approximately 0.9% vitrinite reflectance, and relatively high HI values (kerogen type II-III). Correspondingly, high values of νCHx over γCH indicate a high relative abundance of aromatic rings over aliphatic groups. Moreover, high CH₂/CH₃ ratios suggest long and simple aliphatic chain structures. Molecular data indicate a balanced odd- over even <em>n</em>-alkane distribution and a high amount of long-chain <em>n</em>-alkanes. High Pr/Ph ratios and hopanoid biomarkers reveal an oxidizing depositional environment. The coal seam investigated in this study is characterized by low ash yields and low sulfur contents particularly in the central part of the seam, while percentages of inertinite are high (up to 54 Vol.-%). This data supports a low water table and oligotrophic, raised bog conditions during deposition in a humid, tropical climate which is consistent with the almost equatorial position of the study area during deposition of the Guaduas Formation. Water was mainly supplied via rainfall leading to overall low ash yields. In contrast, the top of the coal seam is strongly enriched in sulfur revealing that rapid marine flooding ultimately ceased peat accumulation leading to authigenic pyrite formation.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S016651622400106X/pdfft?md5=0678b51a064e43ac5115f21dfd3a7881&pid=1-s2.0-S016651622400106X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141391485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}